Carb Choice

[blazer74]

Hello Quadrajet people, newbe here.  Made it thru security. Here's what I have. Application 1974 K5 Blazer 4x4,  Engine 355, Performer intake, Headers and dual exhaust, cam 214 duration @50, 2000 stall, 4:10 gears, 35" tires, 4500 lbs.   Have 2 carbs on hand other than whats on the truck,  First  17085213 single main air bleed and 17056228 large main air bleeds.    Which one to build. I believe Cliff Likes the later single main air bleed carbs. The 17085213 has .038 idle tubes, the channel restrictions have been drilled to .070 prior to me obtaining the carb. Main air bleeds are .082, .055 bypass air, upper idle bleeds .068, lower .076, had 61s rods and 75 jets, EK 2nd rods.  Other carb 17056228  .032 idle tubes, channels are at .055, large main air bleeds .120 both, bypass air .080, upper idle bleeds .070 lower .076, had 48k rods and 77 jets with DP 2nd rods. Which would be prefered to build. I'm looking at recipe #2. Will be changing  to a 218@ 50 Cam soon from 214@ 50. Also does Cliff's recommended float level of 1/4 also apply to a 4x4. The single air bleed carb using his recipes is that using a .035 tip rod or .026 tip, and last question is the baffle used on some carbs that is attached to the center screws do anything.
I have Cliff,s book and is great. I thought I knew something about these quadrajets untill I read his book, Dang.                                  Thanks Craig

[blazer74]

Make that .086 main air bleeds on the 17085213 not .082. (typo)


Craig

[omaha]

Either carb could be made to work. I dont know, maybe the 1708XXXX carb would be a slightly better choice, but dont go on my recommendations on this one as I am just going on my gut instinct. Makeing a carb wotk on a 4x4 has some little quirks that may make a difference that I might not be aware of. (as far a carb choice goes). Which one has less warpage???  (this may be more of a factor than a number for the unit). If you do a search on here, you can find good 4x4 carb mod info.  1/4 float level is good for the 4x4 along with some other mods that will help control fuel slosh and venting etc. (all on the search function)....(I cant remember it all but if you cant find it, im sure we can help you on this forum as this is a subjrct that comes up frequently). Not sure 100% about the baffle but I think it may not be needed if you do a few other mods to the carb for 4x4 application. All in all, a Q-Jet makes an EXCELLENT choice for a 4x4 carb. Maybe the best choice due to its design. I'm sure others will chime in on this, How 'bout it guys?

[Cliff Ruggles]

For serious off roading, we will block all external venting in the airhorn (except the 3/8 tube) and use a taller front vent.  The POE well vents should be made internal.

Really doesn't matter what carb you start with, use the one in the best shape, and having the features that you need, linkage, fuel inlet location, type of choke, etc.

End result is pretty much the same.  We can supply the needed parts to set the carb up for the application, and upgrade it for this new fuel...thanks...Cliff

[blazer74]

No serious off road stuff, mostly cruising (full convertable blazer).
Going to use the 17085213 singe main air bleed carb. Cleaner looking carb, about the same for warpage.  recipe #2, will try 50m rods and 74 jets to start with. Not sure about the 2ndary rods, have a number of sets to try.
Will call for parts soon.   Thanks Craig

[Cliff Ruggles]

Thanks Craig....Cliff

[blazer74]

Well, There I was putting together my 17056228  3015ABL using recipe #1  for the exception of the ICR's which are already at .055.   Large main air bleeds,  Was going to use 76 jets and 48k rods I know I had but cannot find THEM. I have a set of 52k rods that I can use but not sure if they would be too much rod. I know many of the later Chevy carbs use the 77 jets 52 rod setup but thats not what cliffs book recommends.  I need to get this carb on the truck due to the one on the truck needs help, warped, etc..  Im still going to build the 17085213  0077HPB but need the truck  and have everything I need for the other carb except the 48k rods.
What do you Think.


1974 k5 Blazer 4x4
355,   292 adv   214@50   449lift   Performer intake   Headers and dual 2 1/4 exhaust    Stock 882 heads.
4.10 gears     35" tires.

Recipe 1       Large Main bleeds     ICR's .055   Bypass air .080     Idle holes .090


Thanks   Craig

[blazer74]

Also   2000 stall,   flat tops,   Going to use CH 2nd rods and K hanger

Thanks Craig

[Cliff Ruggles]

We sell jets and metering rods, and drive in airbleeds for those models as well.  When you get time, call the shop and we'll get what you need headed your way.

It's difficult to build them with the factory type metering rods, as most are "K" series and only have .005" of taper on the upper section, which limits adjustment with the APT screw.  The large MAB models are also very lean, even with pretty big jets in them.....Cliff

[blazer74]

Ok. Ordered the parts i need today from the sweet voice on the other end.

Have a few questions to ask Cliff if he has a chance to call me back, if not I will post questions later.

Time to head off to work soon.           Thanks Craig

[blazer74]

Question about power pistons.    On carb 17085213 the power piston arms are angle upward 20 degrees or so and on my other carb 17056228 the arms are straight horizontal

Power piston springs Hp Kit   light blue for 14'"  vac  at idle?

[Cliff Ruggles]

The arms should be level.  Pretty common to find them bent upwards, from previous tampering from uneducated builders trying to richen things up some instead of using the APT system.

All of the springs in our kit will work at 14" vacuum.  I'd use one of the stronger springs, dark blue or green for near stock set-ups.  The orange spring is for big cams and low vacuum, the light blue for moderate size cams in mild performance applications.....Cliff